Furnace construction



Jan- 3l, 1967, K. w. HANSEN ETAL 3,301,546

FURNAGE CONSTRUCTION Filed MarCh 6, 1964 United States Patent O Vania Filed Mar. 6, 1964, Ser. No. 349,806 8 Claims.y (Cl. 26o-43) This invention relates to the construction of furnace linings-in particular open hearth sidewalls and like vertical or upright portions of metallurgical furnaces, to novel refractory units with which to construct such furnace linings-which units provide for simplified installation and improved compensation for expansion of these furnace walls when operated at elevated tempera-tures, and provides this compensation, over an extended lperiod of furnace use, t

d The problems o-f provid-ing adequate relief forexpansion of refractory brick, especially when the brick are chemically basic refractory material such as chrome ore, magnesi-te, mixtu-res thereof and the like, in either burned or unburned condition, are legion. The expansion of such basic brick, of course, occurs at elevated temperatures. There are `many reasons advanced for this expansion but, in large part, they are probably due to mineralog-ical phase change in the refractory itself, oxidation of the metal casing and plates or shims conventionally used in constructing furnace linings of such basic brick; and, simply, thermal exansion, which one expects to occur when a body is raised from room temperature to an elevated temperature, the temperature difference, for example, being well over 2000 or even 3000u F. in an open hearth furnace.

In fabrication `of vertical or upright portions of the lining of a metallurgical Ifurnace, such as in the open hearth (which is herein used as an example for construe tion using-the teachings of this invention), the general practice has been to provide physical arrangements which allow an entire wall to expand upwardly without obstruction. Many vertical joints are provided between brick. Sometimes joints are lfilled with compressible asbestos pads, or cardboard or a like combustible material, in order to accommodate horizontal expansion of the wall or lining section. Some in the art have recognized the difficulties with such construction practices, primary because the expansion due to heating is greatest at the hot face of the brick, whereby the major portion of the wall weight is shifted to the hot ends of the brick. These hot ends are subject to great stresses, because of mineralogical phase changes, etc., all of which severely reduce strength, at least as compa-red to the other or cold end of the brick, i-n addition to the weight of the wall.

Some workers in the art have suggested elimination of the compressive or combustible devices, mentioned above, and substantial elimination o-f metal shims or spacer plates, by fabrication of special case configurations. For example, see United States Patent No. 2,192,642, to R. E. Grifth, which discloses both transver-se and tapered longitudinal corrugations as means of compensating for stress buildup in a refractory lining. It further discolses what is sometimes termed a tie plate construction or conhguration for a plate. There have been subsequent suggestions for modification of such as the Griffith teachings, including various corrugatio-n configurations and placements thereof; but practically all of them, including Griffith, have worked on the premise that relief must be had Iat the hot face, where pressure initially is greatest. Variation in brick cross-sectional configuration, measuring from hot end to cold end, and tapering corrugations such as in Grith, are examples of prior constructions based on this theory. Such constructions ice can probably be considered one-shot arrangements for compensation for initial dimension change.

It is an object of this invention to provide dynamic accommodation to changing dimensional gradients over an extended period of furnace life. By dynamic, is meant active accommodation over an extended period as contrasted to Vinitial accommodation. It is a further object of the invention to provide for furnace lining construction which compensates for wear back of brick, with commensurate movement of hot face towards cold face, as a furnace campaign proceeds. d

It is a broad obje-ct 0f the invention-to provide for improved furnace lining construction, particularly upright or vertical sections thereof. It is yet another ob ject o-f the invention to provide a novel, metal encased. refractory unit suitable for use in constructing improved metallurgical furnace linings.

Briefly, according to one embodiment of thev invention, there is provided a plurality of elongate brick, of substantially uniform cross sectional dimension from intended cold end to intended hot end. Bothl such ends thus are'identical and, `as contrasted to prior arrangements, simplify construction of linings. The brick are, preferably, burned basic brick of the magnesia-chrome ore type, having about 70% magnesia and about 30% chrome ore. A metal sheath substantially covers at least three, but preferably all four, of the long sides o-f the basic refractory shape. Each end of the metal sheath covering two only of adjacent intersecting long -faces of the refractory shane has substantially identical crimps formed therethrough. In a wall construction using such shapes, crimps in a given brick sheath contact planar faces of two adjacent brick, i.e. two long faces having no crimps. A plurality of interconnected, substantially open, L-shaped passages are thereby formed at regular intenvals through the wall. These passages are of substantially uniform dimension from cold face to hot face before lfurnace operation.

Upon initial heatup, with commensurate thermal ex,- pansion of the hot ends of the brick, the inner or hot ends' of t-he L-shaped passages or slots are closed olf, because of compression of the crimps on the hot ends of the brick. As operation continues and the hot face or end of the brack is eroded or corroded away, lost through spalling etc., in small incremental steps, the hot face comes closer and closer to the cold face. As this progressive movement ofthe hot face occurs, the rear end of the plurality of L-shaped passages is slowly closed, as the rear or cold ends of the brick become increasingly affected by the thermal .gradient through the brick. This slow closing of the rear or cold end of the L-shaped passages is accompanied by progressive compression of the crimps of the cold end of respective brick. The cold end of the brick are always subject to some wall load.

As one can appreciate from the foregoing, all of the brick in a wall, constructed according to this invention, have their rear or cold ends floating, as it were, with respect to each other; and there is a dynamic, that is, active and continual, accommodation to changing dimensional gradient, as brick which make up the wall wear back during a furnace campaign.

Other objects and further features and advantages of furnace lining construction according to this invention will become readily apparent to those skilled in the refractories and rnetallungical arts, by a study of the following detailed description of exemplary wall and Ibrick construction, together with reference to the drawings. In these drawin-gs:

FIG. 1 is a perspective view of the preferred brick construction according to this invention;

FIG. 2 is an end View of a wall constructed of the brick of FIG. 1; 4

FIG. 3 is a side elevation of an upright orvertical course of brick in the wall of FIG. 2, indicative of the initial expansion of the hot face with commensurate thermal expansion of the forward end of the shapes in the wall;

FIG. 4 is a schematic diagram of the vertical course of brick of FIG. 3, as it appears later in a furnace campai-gn (when the hot face has worn back towards the cold face) and indicating provision of continued accommodation `for changing thermal gradient;

FIG. 5 is an alternative brick construction according to this invention; and

FIG. 6 is still another alternative brick construction of a type usable in construction of open hearth roofs and the like.

A basic refractory shape or -brick 10 is shown in FIG. l as encompassed within two overlap-ping, substantially identical, U-shaped metal cases 11 and 12. For rpur-poses of explanation, end 13 is considered the cold end or face and end 14 the lhot end or face. There are crimps formed at each end of the metal casing which covers two adjacent intersecting long faces of the brick 10, i.e.l a crimp 15 and a crimp 16 are formed in the leg 17 of case 12, and 4the crim-ps 18 and 19 are formed in the face or web portion 2t) of case 12.

In FIG. 2, a plurality of the brick of FIG. l is sh-own assembled as in forming a portion of an upright open hearth endwall, for example. Because the brick of FIG. l are square in cross section and symmetrical one end to the other, it makes no difference which end serves as the cold end or hot end in actual installation, thereby 4greatly easing the problem of the bricklayer. Note, we have shown two brick in the top row, one having crimps 15 andV 18, and the next one having crimps 16 and 19 serving at the cold end. Note, also, that crimps at a common end of a lgiven `brick always abut a flat or planar side surface of two adjacent brick. The result is a free-floating wall, with open lpassages from hot face to cold face before furnace heatup. For purposes of eX- planation and to simplify `description of the manner in which dynamic accommodation for changing thermal gradient is provided for by the present invention, we have chosen to describe the open network which extends from hot face to cold face as comprised of a plurality of interconnected L-shaped spaces or passages 25. These L- shaped passages have a vertical and a lhorizontal leg. Aligned series of horizontal legs in vertical courses provide for vertical expansion and vertical legs in horizontal courses provided for horizontal expansion.

In FIG. 3 (which is intended as schematically typical of any vertical course in the wall of FIG. 2), the wall of FIG. 2 is shown as it might appear shortly after heatup. The hot end or face of the wall of FIG. 3 is designated 26 and the cold end or face 27, for purposes of explanation. In this initial condition, the crimps 19 are cornpressed because of thermal expansion of the hot face 26, while the rear crimps 18 remain substantially unaffected, assuring continued existence of the rear opening of the L-shaped passages 25. FIG. 4 is schematically indicative of the wall of FIG. 3 at a latter stage in a furnace campaign. The hot face 26 is shown closer to the cold face 27, because of wearing away of hot ends of brick which make up the wall. The rear crimps 18 are shown somewhat compressed, because of the changing position of load or wall weight due to a new dimensional gradient, 4but they still vmaintain open L-shaped passa-ges adjacent the cold face 27.

In actual industrial tests of usage of furnace wall construction according to this invention, a furnace came off the line at slightly over 300 heats due to roof problems. The wall of the invention showed no bulging, sagging or other signs of distress, and was put back in service. With comparative prior constructions, after 200 to 25() heats, veneering with additional brick and shimming was usually necessary to obtain further furnace li-fe without wall rebuilding.

Cir

With the construction of FIGS. l through 4, we have shown and discussed brick or shapes which are square in cross section from one end to the other. Of course, brick of alternative cross sectional configurations can be fabricated using the concepts of this invention. Howeve r, it is preferable that there 'be substantially uniform cross sectional dimension from one end to the other. Such an alternative construction is FIG. 5, in which a refractory block 30 is shown encased within a pair of substantially identical overlapping U-shaped metal cases 31 and 32. The outer case 32 has the crimps formed in it. These crimps are formed at each end of the brick through two adjacent and intersecting sides of the case. For example, the web portion 33 of the case which extends between case legs 34 and 35 has a pair of crimps 36 andl 37 formed at one end, with a symmetrical pair of crimps 38 and 39 formed at the other end.l The case side leg 35 has symmetrical crimps 40 and 41 formed at opposite ends.

FIG. 6 is still another construction utilizing the concepts of this invention, in which a refractory block 50 is `provided with a pair of overlapping U-shaped metal cases 51 and 52, the case 52 having cri-mps formed according to the concepts of this invention. These are: crimps 53 and 54 in the web portion 55 of case 52, and crimps 56 and 57 in the leg'58 of the case 52.

Formed through the top of the refractory block 50 is a generally L-shaped aperture, depression, or what have you, 60, arranged to receive or to besuspended upon a conventional hanger device of the type used in constructing open hearth roofs. An exemplary T-shaped hanger, with which these brick can be used, can be found, for example, disclosed in the United States Patent No. 2,304,170 of Heuer. While we have herein disclosed this exemplary han-ger arrangement, brick construction according to this invention is applicable to practically any of the many other conventional suspending arrangements.

From the foregoing discussion, it is clear that the present inventionv represents a departure from the prior art premise that expansion allowance is necessary or must be provided at the hot face. The present invention provides physical means for dynamic accommodation of expansion at both the hot face and cold face, whereby changing dimensional gradients, during an extended furnace canpaign, can be accommodated.

We have discussed the present invention relative to an open hearth, a specific embodiment being an upright wall such as an endwall of an open hearth, and also pointed out its utility in fabrication of open hearth roofs. The novel features of this invention are equally applicable to other types of constructions. For example, it can guarantee uniform and substantially exact precalculatable expansion allowance in the construction of rotary kilns and the like. Provision of substantially uniform and continuing rexpansion allowance from one end of a brick to the other, during an extended furnace campaign, can be an extremely important factor in obtaining longer furnace life. A case in point is the actual commercial testing of this inveniton, which is discussed above.

The metal cases shown in the various drawings are preferably physically attachedl to, or held in place by, the respective encompassed refractory shapes. The manner in which they are attached is not too important, and can be of any of a variety of different ways. For example, one can punch ears through the cases into the body of the brick. Dimples can be pressed through the cases into preformed depressions in the brick body. The cases lcan be glued to the brick since, in service, the brick will expand and obtain a very tight fit within the enveloping'case. We prefer the two case sections be spot welded'toeach other.

Having thus described the inventionin detail and with sufficient particularity as to enable those skilled inthe letters patent is set forth inthe following claims. v l

We claim:

1. A metallurgical furnace lining or Wall at least a portion of which is constructed of a plurality of substantially identical refractory shapes, said shapes having intersecting plan-ar side surfaces extending between two opposed faces, each shape having an -oxidizable case extending substantially from one face to another over at least two intersecing adjacent side surfaces, said shapes being substantially uniform in cross section from one face to the other, there being at least one expansion crimp formed at each end -of each of the portions of the metal cases covering said adjacent side surfaces, all crimps in each .shape being contiguously positioned adjacent a fiat side surface of -an adjacent shape, said wall thereby characterized by a plurality of interconnected generally L-shaped passages of uniform dimension from one side of the wall to the other before furnace heatup.

2. A metallurgical furnace lining or wall at least a portion of which is constructed of a plurality of substantially identical basic refractory shapes, said shapes having intersecting planar side furnaces extending between two opposed faces, each shape having an oxidizable case extending `substantially from one face to another over at least two intersecting adjacent side surfaces, vsaid shapes being substantially uniform in cross section from one face to the other, there being at least one expansion crimp formed at each end of each of the portions of the metal cases covering said adjacent side surfaces, all crimps in each shape being contiguously positioned adjacent a flat side surface of an adjacent shape, said wall thereby characterized by a plurality of 1 interconnected, generally L-shaped passages of uniform dimension from one side of the wall to the other before furnace heatup.

3. The wall o-f claim 2 in which the shapes have four side surfaces all four of which are covered by oxidizable metal casing.

4. The wall of claim 2 in which the shapes are all substantially square in cross section from one end to the other.

5. The wall of claim 2 in which all of the shapes are substantially rect-angular in cross section fr-om one end to the other.

6. The wall of claim 2 in which each of said shapes has means adjacent one face arranged to cooperate with hanger 4means for suspension to form a furnace roof.

7. The w-all of claim 2 in which there is a plurality of crimps formed at each end of at least one of the oxidizable cases which cover said at least two intersecting adjacent side surfaces.

8. The wall of claim 2 in which opposed faces and adjacent cases of each of the shapes are symmetrical with respect to each other.

References Cited by the Examiner UNITED STATES PATENTS 2,216,813 10/ 1940 Goldschmidt 266-43 2,606,017 8/1952 Longenecker 266-43 2,736,187 2/1956 Coffman et al 266-43 FOREIGN PATENTS 191,447 8/ 1957 Austria.

620,003 5 1961 Canada.

660,572 4/ 1963 Canada.

JOHN F. CAMPBELL, Primary Examiner.

I. M. ROMANCHIK, Examiner. 

1. A METALLURGICAL FURNACE LINING OR WALL AT LEAST A PORTION OF WHICH IS CONSTRUCTED OF A PLURALITY OF SUBSTANTIALLY IDENTICAL REFRACTORY SHAPES, SAID SHAPES HAVING INTERSECTING PLANAR SIDE SURFACES EXTENDING BETWEEN TWO OPPOSED FACES, EACH SHAPE HAVING AN OXIDIZABLE CASE EXTENDING SUBSTANTIALLY FROM ONE FACE TO ANOTHER OVER AT LEAST TWO INTERSECING ADJACENT SIDE SURFACES, SAID SHAPES BEING SUBSTANTIALLY UNIFORM IN CROSS SECTION FROM ONE FACE TO THE OTHER, THERE BEING AT LEAST ONE EXPANSION CRIMP FORMED AT EACH END OF EACH OF THE PORTIONS OF THE METAL CASES COVERING SAID ADJACENT SIDE SURFACES, ALL CRIMPS IN EACH SHAPE BEING CONTIGUOUSLY POSITIONED ADJACENT A FLAT SIDE SURFACE OF AN ADJACENT SHAPE, SAID WALL THEREBY CHARACTERIZED BY A PLURALITY OF INTERCONNECTED GENERALLY L-SHAPED PASSAGES OF UNIFORM DIMENSION FROM ONE SIDE OF THE WALL TO THE OTHER BEFORE FURNACE HEATUP. 